Digital transmission technologies such as Digital Video Broadcasting—Terrestrial (DVB-T) for Europe, and Integrated Services Digital Broadcasting—Terrestrial for Japan, have brought TV broadcasting into the digital age. In parallel, the development of the Internet network, and especially the generalization of broadband access offer the technical possibility of broadcasting audio and video services on this network towards terminals. The emerging DVB-H standard corresponds to an additional step with respect to the DVB-T standard, making it possible for mobile terminals to receive digital wireless broadcasting.
The planning of DVB-H networks, as early as the design stage, requires giving consideration to characteristics of conditions of use particular to TV reception by a portable, mobile receiver. Like mobile telephony, consideration must be given to the fact that such uses are chiefly made inside buildings and when on the move.
Within a network, the electric radio signals received by a receiver are often made up of several instances of the transmitted signal. This is the case in particular when the close environment of the transmitter or receiver contains obstacles and when multiple paths are needed (e.g. communication with a cell-type mobile). It is also the case when the same signal is broadcast from several transmission points (paging network in a digital paging system of ERMES type, digital broadcasting networks, or transmission diversity . . . ). As a result, technical devices must be developed to take these phenomena into account.
OFDM technology is largely deployed in multi-frequency networks on account of the desired high bit-rates in digital wireless broadcasting technologies: this is case with DVB for its terrestrial components (DVB-T) and mobile components (DVB-H), and with DAB (Digital Audio Broadcasting) and DMB technologies (Digital Multimédia Broadcasting). Since the various receiver devices are limited by their sensitivity in receiving the different effective components of the signal in a given same integration time, it is advisable to use OFDM modulation. This modulation, between each symbol, provides for a non-data carrying delay allowing integration on reception of all the signals received, provided there are no excessively delayed signals. It will be understood therefore that with OFDM technology some areas offer insufficient communication quality due to interference resulting from late reception of signals transmitted via “delayed” paths.
In the “young” prior art, tools are known for managing broadcasting transmitters requiring case-by-case adjustment. These tools sometimes enable visualization of maps of interference generated by differences in propagation time, and thereby provide information which can be used to <<manually>> adjust delays to eliminate interference.
At the current time there does not exist any satisfactory solution for managing delays which cause interference in a television broadcasting radio network, and it is difficult for an operator to ensure acceptable quality of service with existing tools.